1. Technical Field of the Invention
The present invention relates to a direct intake port and a helical intake port both used for various kinds of engines such as a diesel engine, a gasoline engine or a gas engine.
2. Preamble Structure
The direct intake port for an engine according to the present invention is directed to those each of which has the following preamble structure, for example, as shown in FIG. 1(A) to FIG. 1(E) (present invention) or FIG. 8(A) to FIG. 8(C) (prior art).
FIG. 1(A) to FIG. 1(E) show a direct double intake port for an engine according to the present invention. FIG. 1(A) is a cross sectional plan view. FIG. 1(B) is a vertical sectional front view of a first direct intake port 2A. FIG. 1(C) is a sectional view taken along a line C--C in FIG. 1(B). FIG. 1(D) is a vertical sectional front view of a second direct intake port 2B. FIG. 1(E) is a sectional view taken along a line E--E in FIG. 1(D).
FIG. 8(A) to FIG. 8(C) show a conventional direct double intake port for an engine. FIG. 8(A) is a cross sectional plan view. FIG. 8(B) is a vertical sectional front view of a first intake port 102A. FIG. 8(C) is a vertical sectional front view of a second intake port 102B.
An engine has a cylinder head 1, 101 provided with a direct intake port 2, 102. This direct intake port 2, 102 is formed by communicating a port inlet 3, 103 with a port outlet 7, 107 through a port upstream portion 4,104, a port bent portion 5,105 and a port downstream portion 6, 106 in order. This port outlet 7, 107 is opened at a position eccentric from a cylinder axis 10, 110 of an upper end surface 9, 109 of a cylinder chamber 8, 108.
3. Prior Art
FIG. 8(A) to FIG. 8(C) show an example of conventional shapes of the bent portion 105 of the direct intake port 102 in the preamble structure.
FIG. 8(A) to FIG. 8(C) illustrate a conventional direct double intake port for a vertical diesel engine. FIG. 8(A) is a cross sectional plan view. FIG. 8(B) is a vertical sectional front view of a first intake port 102A. FIG. 8(C) is a vertical sectional front view of a second intake port 102B.
The bent portion 105 is formed so as to only smoothly continue the upstream portion 104 with the downstream portion 106. Therefore, it flows an intake air current (A) from the upstream portion (104) to the downstream portion (106) smoothly.
The prior art has the following problems.
As is well known, the direct intake port is formed by putting importance on the increase of volumetric efficiency. Accordingly, there is produced insufficient swirl within the cylinder chamber 108, which results in a disadvantage of failing to mix air with fuel satisfactorily.
The smoothly continued shape of the bent portion 105 of the conventional direct intake port 102 shown in FIG. 8(A) to FIG. 8(C) cannot improve the disadvantage of producing insufficient swirl the direct intake port 2 has by nature